Mycena rubrofusca J. W. Guo, Z. W. Liu, Y. P. Ge & Q. Na, 2025

Guo, Jingwen, Liu, Zewei, Zeng, Hui, Ge, Yupeng & Na, Qin, 2025, Three new species of Mycena sect. Calodontes (Mycenaceae, Agaricales) from Northeastern China, MycoKeys 125, pp. 51-79 : 51-79

Mycena rubrofusca J. W. Guo, Z. W. Liu, Y. P. Ge & Q. Na , sp. nov.,

Figs 9 , 10 , 11

Diagnosis.

Pileus light reddish-brown to light grayish-brown, near margin hygrophanous. Pleurocystidia and caulocystidia absent. Differ from M. polycystidiata Z. W. Liu, Y. P. Ge, L. Zou & Q. Na by having pleurocystidia and caulocystidia.

Holotype.

China • Heilongjiang Province, Mudanjiang City, Mudanfeng National Forest Park , 42°45'74"N, 128°14'41"E, 22 August 2024, Jingwen Guo, Tian Wang, Qin Na, Zengcai Liu, Ruipeng Liu, Pengyu Du, Ying Yu, and Yupeng Ge leg., FFAAS 3406 (collection no. NJ 6508 ) .

Etymology.

Name refers to the light reddish-brown, light grayish brown to brown pileus.

Description.

Pileus 17–26 mm in diam., hemispherical, plano-convex at mature, margin wavy; Light Drab ( XLVI 17 ′′′′ b) at center, gradually towards margin to Light Vinaceous-Fawn ( XL 13 ′′′ d), Pale Ecru-Drab ( XLVI 13 ′′′′ f) to * Drab-Gray ( XLVI 17 ′′′′ d), margin Light Drab ( XLVI 17 ′′′′ b) to * Drab ( XLVI 17 ′′′′); striate * Drab ( XLVI 17 ′′′′), towards the center up to 1 / 8–1 / 7 diam.; surface moist, near margin hygrophanous. Context White ( LIII), 1.0 mm thick, fragile. Lamellae adnexed or subdecurrent, approximately 38 reaching the stipe, 1–3 tiers of lamellulae, White ( LIII), irregularly intervenose, stretching downward to 2 / 3–3 / 4 of the width of lamellae, edge concolorous, wavy. Stipe 44–45 × 2–4 mm, central, cylindrical; apex to lower part Vinaceous-Drab ( XLV 5 ′′′′), Light Brownish Drab ( XLV 9 ′′′′ b) to * Hair brown ( XLVI 17 ′′′′ i), base Light Grayish Olive ( XLVI 21 ′′′′ b), hollow, fragile; base swollen, sparse White ( LIII) pubescent at base. Odor and taste faintly raphanoid.

Basidiospores (40 / 2 / 2) (5.1) 6.2– 7.4 – 8.5 (8.8) × (3.8) 4.0– 4.6 – 5.5 (5.7) μm [ Q = (1.52) 1.55–1.84 (1.89), Q m = 1.69 ± 0.10] [ holotype (20 / 1 / 1) (6.8) 7.2– 7.6 – 8.3 (8.5) × (3.8) 4.1– 4.6 – 4.8 (5.0) μm [ Q = 1.60–1.81, Q m = 1.70 ± 0.08], ellipsoid to narrowly ellipsoid, colourless, smooth (1000 ×), thin-walled, amyloid. Basidia clavate, 16–28 × 5–8 μm, hyaline, thin-walled, 4 - spored, sterigmata 2–4 μm in length. Cheilocystidia utriform, clavate, 24–67 × 8–23 μm, thin-walled, smooth. Pleurocystidia absent. Pileipellis a cutis composed of cylindrical cells, 28–76 × 5–15 μm, smooth, thin-walled; terminal cells cylindrical, apex tapering, 33–75 μm in length, apex 2–9 μm, base 3–11 μm, thin-walled, hyaline. Hypodermium formed by fusiform to subglobose hyphae, 26–84 × 11–34 μm, thin-walled, hyaline. Lamellar trama subregular, dextrinoid. Stipitipellis a cutis composed of cylindrical hyphae, 6–16 μm in diam, smooth, thin-walled; projecting terminal cells cylindrical or fusiform, 31–73 × 4–9 μm, thin-walled, smooth, hyaline; caulocystidia absent. Clamps present in all tissues.

Habit and habitat.

Scattered on the litter layers in Fraxinus mandschurica Rupr. , Pinus koraiensis , and Tilia amurensis Rupr. mixed forests during summer and autumn.

Known distribution.

Heilongjiang Province, China.

Additional material examined.

China • Heilongjiang Province, Hegang City, Taipinggou National Nature Reserve , 48°12'43"N, 130°66'04"E, 3 September 2021, Zewei Liu, Qin Na, Shixin Wang, and Yupeng Ge leg., FFAAS 3407 (collection no. MY 0793 ) .

Notes.

Mycena polycystidiata is the closest species to M. rubrofusca because it has a light grayish-brown to brown pileus and stipe, and utriform cheilocystidia, but M. polycystidiata has pleurocystidia and caulocystidia ( Liu et al. 2022). Mycena pura , a widely distributed species in the North temperate zone, differs from M. rubrofusca by its fusiform, clavate, or subglobose cheilocystidia and pleurocystidia, and clavate or conical caulocystidia ( Maas Geesteranus 1992 a, 1992 b; Perry 2002; Robich 2003; Thormann et al. 2006; Aronsen and Læssøe 2016; Na 2019; Okon et al. 2022; Liu 2023). Due to the light gray-brown to light brown pileus, M. variispora Shun Liu & Biao Zhu and M. subbrunnea Shun Liu & Biao Zhu are difficult to distinguish from M. rubrofusca , but they can be distinguished by the occurrence in mixed forests of Larix gmelinii and Betula platyphylla , purple lamellae, and clavate, thick-walled cheilocystidia ( Liu et al. 2024). Mycena pearsoniana differs from M. rubrofusca in having purple pileus and clavate or fusiform caulocystidia ( Smith 1947; Dennis 1970; Kost 2002; Harder et al. 2012; Aronsen and Læssøe 2016; Na 2019; Kwon et al. 2020). Mycena rufobrunnea Z. W. Liu, Y. P. Ge & Q. Na and M. vinacea Cleland , which were reported from northeastern China and southern Australia, respectively, both resemble M. rubrofusca in having utriform cheilocystidia ( Cleland 1931; Liu et al. 2022). However, both of them also have clavate cheilocystidia; M. rufobrunnea is distinguished by a light brown to reddish-brown pileus, whereas M. vinacea is characterized by cylindrical pleurocystidia and basidiospores ( Cleland 1931; Liu et al. 2022).

Figures

Figure 9. Basidiomata of Mycena rubrofusca. A – E. Collection FFAAS 3406, holotype; F – J. Collection FFAAS 3407. Scale bars: 15 mm (A – B, F – G); 1 mm (C – D); 5 mm (E, H – J). Photographs (A – J) by Jingwen Guo and Yupeng Ge.

Figure 10. Microscopic features of Mycena rubrofusca (FFAAS 3406, holotype). A – E. Basidiospores; F. Basidia; G – R. Cheilocystidia; S. Pileipellis and hypodermium; T. Lamellar trama; U. Stipitipellis. Bars: 5 μm (A – E); 15 μm (F, T, U); 25 μm (G – R); 30 μm (S). Structures (A – E) were rehydrated in 5 % KOH aqueous solution and (F – U) were stained in 1 % Congo red aqueous solution.

Figure 11. Morphological features of Mycena rubrofusca (FFAAS 3406, holotype). A. Basidiomata; B. Basidiospores; C. Basidia; D. Cheilocystidia; E. Stipitipellis; F. Pileipellis and hypodermium. Scale bars: 15 mm (A, C, E – F); 5 μm (B); 25 μm (D). Drawings by Jingwen Guo.